(A) Hydraulically equivalent compensatory storage shall be provided for any regulatory floodway storage lost due to the proposed work from the volume of fill or structures placed and the impact of any related flood control projects.
(B) Compensatory storage for fill or structures shall be equal to at least one and one-half times the volume of floodplain storage lost.
(C) Artificially created storage lost due to a reduction in head loss behind a bridge shall not be required to be replaced.
(D) The compensatory regulatory floodway storage shall be placed between the proposed normal water elevation and the proposed 100-year flood elevation. All regulatory floodway storage lost below the existing ten-year flood elevation shall be replaced below the proposed ten-year flood elevation. All regulatory floodway storage lost above the existing ten-year flood elevation shall be replaced above the proposed ten-year flood elevation. All such excavations shall be constructed to drain freely and openly to the watercourse and preferably located adjacent to the development.
(E) If the compensatory storage will not be placed at the location of the proposed construction, the applicant’s engineer shall demonstrate to IDNR-OWR through a determination of flood discharges and water surface elevations that the compensatory storage is hydraulically equivalent.
(F) Finally, there shall be no reduction in floodway surface area as a result of a floodway modification, unless such modification is necessary to reduce flooding at existing structure.
(G) The fill material shall be homogeneous and isotropic and compacted to at least 95% (Standard Proctor).
(H) Finished grade shall be 4: 1 maximum and 1% minimum. Retaining walls, excluding control structures, are not permitted below the BFE.
(I) Adequate protection is required for fill slopes exposed to floodwaters with expected velocities during the occurrence of the base flood of 5 fps or less by covering them with vegetation undergrowth (grass, vines, etc.).
(J) Adequate protection is required for fill slopes exposed to floodwaters with expected velocities during the occurrence of the base flood greater than 5 fps by covering them with stone or rock slope protection or other material acceptable to the village.
(Ord. 3187, passed 1-22-19) Penalty, see § 152.999